The present invention relates to a mechanism for bending an elongated body, and more particularly, to a mechanism for bending an elongated body suitable for use in an endoscope or the like.
A wide variety of endoscopes have heretofore been available, all of which include bendable elongated body portions, for observing the interior of various organs such as blood vessel, coelomata, and the like. Various mechanisms for bending such an elongated body will be considered.
As illustrated in FIG. 1, one well-known mechanism, as disclosed in Japanese utility model publication No. 13033/1974, includes a bending tube 62 composed of a multiplicity of nodal rings 61, the central portions of which are formed with fulcrum portions 60 and encasing a segment of fiber 63, and a several of wires 64, first ends of which are fixed to a nodal ring 61 disposed at the tip portion thereof, the wires 64 being inserted through other nodal rings 61. Another well-known bending mechanism, as disclosed in Japanese laid-open patent publication No. 25140/1983, is composed of a multiplicity of articulated pieces, shape-memorizing alloys provided between the articulated pieces, and a heating device for bending the shape-memorizing alloys in predetermined shapes by heating them with a supplied electric current.
The above-described mechanisms for bending an elongated body function by manipulating the wires and heating the shape-memorizing alloys by the heating device, thereby bending the multiplicity of nodal rings or articulated pieces. The tip portion of the elongated body can be bent at a predetermined angle, which permits observation of desired portions within a vascular tract or the like.
Because, however, the former type of mechanism for bending the elongated body includes a multiplicity of nodal rings and wires required for the bending operation, the structure is complicated. It is therefore difficult to reduce the diameter of the elongated body, resulting in a limitation in the observable diameter of the organ or the like. Consequently, there arises a problem in that ulcers, tumors or the like cannot be detected in their early stages. The amount of bending of the elongated body is adjusted in accordance with the degree to which the wires are moved when observing various organs. Hence, this adjustment leads to problems wherein the operation of bending the elongated body becomes intricate and it is difficult to bend the body at a desired angle with high accuracy.
The latter type of bending mechanism is accompanied by problems in addition to those inherent in the former bending mechanism because of the provision of the multiplicity of articulated pieces. To be specific, since the device for heating the shape-memorizing alloy employs an electrically energized heating system, when the elongated body is employed as an endoscope, there may be a danger of electric shock. The practical applications of such an arrangement are restricted.